Why does my dog chew his hair off in the summer?

Your dog may have a skin disease or an allergy that is exacerbated by summertime elements. He may have anxieties about something that happens only in the summer. Take him to the veterinarian to make sure he doesn't have anything physically wrong. Then you can try to address his psychological state.

This sounds like an allergy to either grass or pollens. It may be accompanied by scratching, and raw/irritated skin but no fleas or mites are apparent. Natural treatments are available or your vet may prescribe cortisone.

It can be a number of different reasons. There might be small flies biting at his skin, he could just be really hot and irritated and so he chews, he could have dry skin due to the weather change, he could be allergic to something that only comes out in the summertime... the sky is the limit.